PqqE gene as a molecular marker of phosphate solubilizing bacteria associated to peanut plants.

ANZUAY, M.S.; DALMASSO, R.; TAURIAN, T.; LUDUEÑA, L.; ANGELINI, J.G.; CHIATTI, M.H.; FERNANDEZ VALDÉS, P.

Los Cocos

Congreso; XVIII SAMIGE; 2022

In Argentinian peanut agricultural area, low values of soil phosphorus (P) were detected. Within soil bacteria, some are capable of exercise beneficial effects for plants growth, for example the solubilization of insoluble phosphates that providing P to plants. This nutrient can be released from inorganic phosphorous compounds by the synthesis of organic acids such as gluconic acid (GA). The production of GA is the main mechanism by which Gram-negative bacteria solubilize insoluble inorganic soil P sources. This organic acid is produced by phosphate solubilizing bacteria (PBS) by the action of glucose dehydrogenase (GDH)-PQQ holoenzyme. The role of PQQ cofactor in this oxidative pathway is essential. Previous results from our laboratory indicated that a large number of Gram-negative PSB contain in their genome the pqqE gene, one of the essential genes involved in PQQ biosynthesis. Besides, the presence of this gene was detected in PSB from mixed samples of bacterial cultures. The objective of this study was to analyze the presence of pqqE gene in rhizospheric soil samples in presence and absence of peanut plants and inoculated or not with PSB. DNA was isolated from samples of rhizospheric soil associated to fields of peanut plants from Río Cuarto (SRRC), San Severo (SRSS), La Carlota (SRLC), Reducción (SRR), Gigena (SRG), San Ambrosio (SRSA). Also, rhizospheric soil samples obtained from a microcosms assay with peanut plants growing in SRRC inoculated (SRPI) or not (SRPNI) with SS-ER-24 strain were analyzed. SRRC without plants and inoculated with SS-ER-24 strain (SRI) and non-rhizospheric soil were also analyzed (SNR). PCRs-pqqE were performed using two pairs of primers designed in our laboratory. The pair pqqEF-317/1019 that amplify pqqE gene from several bacteria of different genera and the specific pair pqqEPS1/pqqEPS2 designed to amplify the fragment in the genus Pseudomonas. The PCR-pqqE products were sent to Macrogen Inc. laboratories. The expected PCR products of amplification using the specific primers were observed in all soil samples analyzed, with exception of SRLC. On the other hand, by using the pair pqqEF-317/1019 the amplification of the expected fragment was observed in the samples SRRC, SRSS, SRR, SRG, SRSA and SRI. The pqqE sequences from the different samples showed a high identity with sequences of pqqE bacterial gene from genera Pseudomonas in those PCR fragments obtained with specific primers. The sequences of the fragments obtained with degenerated primers showed identity with sequences belonging to the genera Pseudomonas, Serratia, Pantoea, Enterobacter, Klebsiella and Acinetobacter. It is possible to conclude that pqqE gene was detected in rhizospheric and non-rhizospheric soil samples, rhizospheric soil with peanut plants inoculated with BSP and notinoculated. Therefore, the pqqE gene is a potential molecular marker for Gram-negative bacteria with a phosphate-solubilizing phenotype in soil samples.